In the petroleum industry, it is common for substrates to become contaminated with petroleum hydrocarbons. One particular example of a substrate that can become contaminated is ground soil. In industrial areas, it is common for petroleum hydrocarbons to spill onto ground soil during normal drilling or storage operations or while in transit. Over time, repeated spills can result in excessive hydrocarbon accumulation in the ground soil, which can potentially become an environmental hazard. Further, these spilled hydrocarbons are a valuable commodity from which economic value is not being realized. As a result, the industry has traditionally sought improved means for remediating the contaminated ground soils in order to remove and/or recover substantially all of the hydrocarbons contained therein.
Examples of previously used methods for removing petroleum hydrocarbons from contaminated soils include, for example, excavation, microbial remediation, phytoregeneration, thermal desorption, incineration and soil washing; however, these previously used methods have been expensive, difficult or dangerous to use, inefficient and/or have not provided the desired degree of separation of the components in the substrate. Further, none of the previously used methods allow for recovery of petroleum hydrocarbons for refining.
There are also particular disadvantages associated with each of these previously used methods. For example, excavation only changes the location, and not the contaminated nature, of the substrate. Further, the use of indigenous substrate types to refill excavation sites is often not permitted by local regulations. Microbial remediation, also known as bacterial decay, requires months and sometimes years to complete, and is typically ineffective for large areas contaminated to depths greater than a few inches below the surface. Phytoregeneration, i.e., the planting of fast growing leafy vegetation at the site, requires extensive site preparation and cleanup time. Thermal desorption is extremely slow and expensive, and the “cleaned” substrate is typically only clean enough to use as construction fill. Incineration consumes vast quantities of fossil fuel, discolors the substrate and generates large amounts of carbon dioxide, which could potentially violate air quality standard limitations. Soil washing is expensive and results in the creation of a hazardous waste stream. Soil washing also causes the total destruction of the hydrocarbon and creates a hazardous waste stream.
In addition to ground soil, drill cuttings are another example of a substrate that can become contaminated. Drill cuttings are the accumulated mixture of drilling mud, rock fragments, sediment, fluids, solids and/or specialty chemicals produced in connection with the drilling of exploration, appraisal and production wells. Hydrocarbons are often found in these cuttings. Industry has traditionally used large vertical separators such as the VERTI-G™ dryer to reduce the hydrocarbon and water liquid phase from the cuttings; however, dryers are inefficient and/or have not provided the desired degree of separation of components in the substrate. The most efficient dryers leave between 3% and 10% of the liquid phase in the substrate. Further, these separators did not clean the drill cuttings sufficiently to classify the cuttings as non-hazardous waste suitable for dumping or use in other applications.
Thus, there is a need for an efficient and cost effective technique to maximize removal and recovery of petroleum hydrocarbons from contaminated substrates, particularly contaminated ground soils and petroleum drilling cuttings. Also, there is a need for a process for petroleum hydrocarbon recovery from contaminated substrates that utilizes simple or existing equipment. Further, there is a need for a composition that can be added to contaminated substrates to recover substantially all of the petroleum hydrocarbons without resulting in excessive reaction with the contaminated substrate components or damage to the petroleum hydrocarbons.